1. Field of Invention
This invention relates to optical microscopy, and particularly to near-field optical microscopy.
2. Description of Prior Art
Optical microscope is a well-known and widely used instrument. Due to the diffraction limit, its maximum resolution which we are able to get is about 200 nanometers. To observe finer details, other microscopes had been developed, for example, electron microscope, scanning tunneling microscope (STM), and atomic force microscope (AFM), all with sub-nanometer resolution. Electron microscope, STM, and AFM however, can't substitute optical microscope for many applications, especially in biomedical fields because, they lack ability of chemical and molecular identification. Near-field scanning optical microscope (NSOM) utilizes optical near-field effect to break the diffraction limit. It can reach resolution of 50 to 100 nanometers, or nanoscale, which is usually defined as below 100 nanometers. NSOM, on other hand, has its own drawbacks, which include slow imaging speed, operation complexity, and difficulties with soft sample, sample in solution, and dynamic observation. The weakness of NSOM has hampered its usefulness and application ever since it was first made more than twenty years ago.
Accordingly, there exists a need for an optical microscope in many fields, in particular biomedical fields, which breaks the diffraction limit, has a fast imaging speed, is easy to operate, works well with soft sample and sample in solution, and is capable of dynamic observations.